Read the poem and answer the question

Sleep, O sleep
With thy Rod of Incantation
Charm my Imagination,
Then, only then, I cease to weep

By thy power,
The virgin, by Time O' ertaken,
For Years forlorn, forsaken,
Enjoys the happy Hour.

What's to sleep?
'Tis a visionary Blessing;
A dream that's past expressing;
Our utmost Wish possessing;
So may I always keep.

The poem is